Certain jacks or other telescopic actuators are fitted with a device for locking the rod in position, in particular in a retracted position or in an extended position. Locking devices are known that comprise firstly a bushing presenting some number of elastically deformable catches that are cantilevered-out in an axial direction and that are terminated by respective hooks, and secondly an anchor portion including an annular setback for receiving the hooks, the bushing and the anchor portion being mounted on two portions of the actuator that can be moved relative to each other.
For example, the bushing is placed at the end of the cylinder of the actuator, while the anchor portion is secured to the sliding rod of the actuator. The anchor portion includes a step so that when the anchor portion engages under the catches, it causes them to flex. The anchor portion then includes an annular setback to enable the catches to return to their rest position once the hooks have gone past the step, with the hooks then being engaged in the annular setback. A locking sleeve is then moved axially to cover the catches and thus prevent them deforming radially, such that the hooks are held captive in the annular setback. The rod is then locked in position.
In order to unlock the rod, it suffices to move back the sleeve so as to enable the catches to flex once more, and then to cause the anchor portion to move away from the bushing.
That type of locking is particularly effective with hydraulic actuators. The locking sleeve is itself moved by fluid under pressure, in concert with the movement of the rod, without there being any need to provide individualized control therefor. With electromechanical technology, the situation is more difficult. An example of locking using catches is given in document FR 2 895 482. In that document, the locking device is used to prevent an auxiliary rod from moving in a main rod. The locking sleeve is moved axially by means of a rotary electric motor specially provided for moving the locking sleeve, with the rotary movement thereof being transformed via a helical connection into axial movement of the locking sleeve.